1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to an LCD device to improve a picture quality by realizing a rapid response speed, and a method of driving the same.
2. Discussion of the Related Art
Generally, LCD devices adjust light transmittance of liquid crystal cells according to a video signal so as to display images. An active matrix (AM) type LCD device which has a switching element formed for every liquid crystal cell is suitable for the display of moving images. A thin film transistor (hereinafter, referred to as a TFT) is mainly used as the switching element in the AM type LCD device.
However, the LCD device has a relatively low response speed due to the characteristics of the inherent viscosity and the elasticity of liquid crystal, as can be seen from the following equations 1 and 2:
                              τ          r                ∝                              γ            ⁢                                                  ⁢                          d              2                                            Δɛ            ⁢                                                                          Va                  2                                -                                  V                  F                  2                                                                                                      [                  Equation          ⁢                                          ⁢          1                ]            where τr is a rising time when a voltage is applied to the liquid crystal, Va is the applied voltage, VF is a Freederick transition voltage at which liquid crystal molecules start to be inclined, d is a liquid crystal cell gap, and γ is the rotational viscosity of the liquid crystal molecules.
                              τ          F                ∝                              γ            ⁢                                                  ⁢                          d              2                                K                                    [                  Equation          ⁢                                          ⁢          2                ]            where τF is a falling time when the liquid crystal is returned to its original position owing to an elastic restoration force after the voltage applied to the liquid crystal is turned off, and K is the inherent elastic modulus of the liquid crystal.
In a twisted nematic (TN) mode, although the response speed of the liquid crystal may be varied based on the speed of the physical properties and cell gap of the liquid crystal, it is common that the rising time is 20 to 80 ms and the falling time is 20 to 30 ms. Because this liquid crystal response speed is longer than one frame period (16.67 ms in National Television Standards Committee NTSC) of a moving image, the response of the liquid crystal proceeds to the next frame before a voltage being charged on the liquid crystal reaches a desired level, as shown in FIG. 1, resulting in motion blurring in which an afterimage is left in the eyeplane.
With reference to FIG. 1, a related art LCD device cannot express a desired color and brightness for display of moving images in that, when data VD is changed from one level to another level, the corresponding display brightness level BL is unable to reach a desired value due to a slow response of the liquid crystal display device. As a result, the motion blurring occurs in the moving image, causing degradation in contrast ratio and display quality.